1. Field of the Invention
This invention relates to the rolling of elongated metal sheet and strip workpieces (hereinafter "strip") in a rolling mill stand having at least one set of upper and lower work rolls and wherein, during rolling, the work rolls are rotated around their respective longitudinal axes and, at the same time, are continuously shifted along those axes. Online work roll grinding, rehardening and cooling are performed outside the mill stand.
2. Description of the Prior Art
In conventional rolling mills, the work rolls are engaged in circular motion in respect to the rolled strip. During such rolling, the deformation in the roll bite (the vertical spacing between the work rolls) is basically two-dimensional. This is due to the frictional forces acting in the roll axial direction between the work rolls and the rolled product. In such conventional rolling process, the tonnage of product rolled between work roll changes is limited due to roll wear, roll marks, and deterioration of the roll surfaces due to fire cracks and banding. In order to reduce such roll problems, and/or to aid in strip profile and shape control during rolling, axial work roll shifting has been commonly used. Prior art patents exemplifying work roll shifting include: U.S. Pat. No. 4,711,116 (work roll shifting and bending); U.S. Pat. Nos. 4,864,836; 4,898,014; 4,934,166; 4,955,221; 5,640,866 (roll shifting and bending), and U.S. Pat. No. 5,655,398 (roll shifting and crossing). U.S. Pat. No. 5,165,266 shows a checkless roll support mechanism by means of which the work rolls may be balanced, bent in the upstream or downstream horizontal direction or vertically upwardly or downwardly, crossed or off-set.
The equipment for carrying out such conventional rolling also may be provided with online roll grinders inside the mill housing, between the drive side and the operator side of the rolling mill. Such roll grinders operate in a hostile, high temperature, corrosive environment and, consequently, do not provide accurate roll grinding. Conventionally ground work rolls are lubricated and cooled, but the amount and quality of lubricant/coolant fluid is not optimum for grinding, but rather for cooling only. Moreover, to grind the work rolls properly, it is necessary to know accurately the position of the grinding tool. In conventional grinding, inside the mill housing, the environment is a poor one for such accurate measurements. Still further, the work roll thermal crown fluctuates so that the dimensions of the work rolls change--further interfering with accurate grinding.